1) Field of the Invention
The present invention relates to a cover of traps or manholes equipped with a mechanism for lifting and horizontally translating the cover.
In particular, the present invention deals with the field of covers of manholes or traps, also governed by UNI EN 124/1995 standard related to crowning and closing devices for circulating areas used by pedestrians and vehicles.
2) Background Art
Currently, the majority of such devices is of the cast iron type, whose movements are performed by means of manual lifting tools. Since such covers generally are more than 25 kg heavy, it is necessary to have two or more operators in order to perform such movements or to use a suitable working tool. Recently, covers have been devised which are hinged in one or more points: in this latter case, the cover is also made with many sections, and its handling is performed by rotating the cover upwards. Such arrangement provides for the sole use of cast iron covers. The type of filling covers, especially if having big sizes (greater than 70 cm by 70 cm), has the problems of having a great weight (more than 100 daN), of being generally custom built with a frame and hooks for performing cover movements, which can occur only through the use of suitable working tools (lifting trucks, mechanical blades, etc.). A variation in commerce consist in a filling cover hinged on one side, whose opening occurs with the help of some gas springs below the cover, whose function facilitating its lifting.
Summarizing, the trap covers ordinarily used have the following inconveniences:
1. They have reduced sizes linked to the need of reducing their weight
2. Are mainly made of a material (cast iron), different from the surrounding pavement
3. Have weight and shape not compatible with safety standards related to manual handling of loads (weight>25 daN with the risk of squashing lower limbs, in addition to the risk of fall of the cover into the trap, if it opening is not circular)
4. Big-sized covers cannot be manually handled
5. Their great weight has an incidence of transport costs.